I LOVE zombie movies, but here is the whole problem with the zombie theory. It wouldn't spread like you think it would. In every zombie movie, the zombies are super hungry, and want nothing but flesh. So once there were 10-20 zombies, they wouldn't be making a whole lot more, because whoever they caught would get picked CLEAN. There wouldn't be anything left to turn into a zombie.

Walking Dead explains. Zombies don't actually eat for nourishment. As such, they don't need to eat flesh, they're only compelled to eat flesh. The only flesh they're compelled to eat, in the Walking Dead, is flesh that is living or very fresh. So, in effect, once the victim dies, they start to "turn off" from eating the victim. I do agree that there would be way more zombies that are half eaten (possibly missing legs/arms/etc...).

__________________In this world of sin and sorrow there is always something to be thankful for; as for me, I rejoice that I am not a Republican.
- H. L. Mencken